The purpose of this project is to facilitate the development of adjunct hyperthermia modalities for cancer treatment by theoretically and experimentally studying the spatial and temporal variation in the temperature field of tissues subjected to microwave and radio-frequency electro-magnetic radiation. Currently, we are mathematically modeling the electromagnetic energy deposition characteristics and resulting thermal profiles of human extremities subjected to RF irradiation from various types of helical coil applicators. We are also conducting experimental measurements of the thermal profiles of various types of phantoms subjected to RF irradiation from various types of helical coil applicators. We have found (1) that helical coil applicators operating under self-resonant conditions can produce deep, relatively uniform and stable heating in fat-muscle phantoms and (2) that they should be able to locally raise the temperature of an extremity to the therapeutic temperature range of 42-45 C. In preparation for developing a clinically useful system, our coil design, phantoms, and bio-heat transfer model are currently being optimized.